Microservice Migration: A Step-by-Step Guide

When too many people are working on a single tightly coupled codebase, as is normal in monolithic applications, bottlenecks are a usual challenge together with reliability and scaling problems.

This is why, a Statistics survey says that 85% of respondents of large organization have migrated to a loosely coupled microservices architecture.

While this could be interpreted as bigger organizations are the ones gaining benefits from microservices, this is far from the truth. Smaller companies can also benefit from a microservices architecture and in fact many already do so.

If your organization is considering migrating partially or fully from a monolith to microservices, this article is for you. It provides insights into the steps needed for a successful transition.

Step 1: Assess Readiness for Migration

A successful migration requires analyzing the current infrastructure, internal policies, and team competence. Some of the points needing your attention include:

• Core business priorities. Determine what you want to gain after moving to microservices. It could be rapid development, increased uptime, innovation, or scalability.
• Team structure. Microservices require effective communications and autonomy from teams. It means you must assess the tools for collaboration and a governance model in your organization.
• Infrastructure readiness. The loosely-coupled architecture allows you to shorten your release cycles to bring more value to customers. So, consider what tools and methods you use to deploy services and how you can remediate them after failed deployments.
• DevOps competence. Your teams should understand the fundamental practices of DevOps and have the right tech to maximize organizational agility in microservices.
• Security measures. Cybersecurity is critical for microservices architecture, and you must consider it for every isolated system. Assess your authorization and authentication measures, API gateways, communication protocols, network security protocols, and firewalls.

Step 2: Identify Functions and Dependencies

In monolithic architectures, code often piles up, making it too complex and full of hidden dependencies. For example, code for a payment service can go to external payment providers, load irrelevant libraries, or hit retired processes.

Start by inventorying your functions and business capabilities. Each microservice must serve a specific function and have a single data repository. So, you must retire applications that duplicate each other’s functionality or provide similar data from multiple locations.

Step 3: Select Migration Candidates

Determine which bounded contexts (functional groups) provide the most value as microservices and which you should leave in the monolith system for the time being.

The developers will give you insights into the existing implementations, dependencies, and internal events. The non-technical experts will tell you about things missing in your services or features that might be critical in the future.

Step 4: Prioritize Services for Migration

You need to identify components to move first. Start with edge services — bounded contexts with fewer dependencies that are likely to be easiest to decompose into smaller services. These could include order management, invoicing, or notification features.

You might also migrate monolith to microservices to address problems like performance bottlenecks.

Step 5: Select a Scalable Infrastructure

Here, you can use certified cloud providers like Google Cloud, Microsoft Azure, and Amazon Web Services.

They let you easily scale resources for microservices and even support autoscaling. Flexible pay-as-you-go billing means you don’t pay for the resources you don’t use. You also get secure communication protocols and authorization tools to safeguard your data. Additionally, the providers take care of the infrastructure maintenance for you.

Step 6: Separate the Application’s Layers

When migrating to microservices, you need to separate the presentation, business logic, and persistence (data) layers of your monolithic applications.

As you divide the layers, you’ll need to set up gateway APIs that route requests between the client and the backend. The API sets the boundaries between layers, helping your teams decouple and isolate the application.

Step 7: Set Up Communications

Effective communication ensures exchange between different services in the loosely coupled architecture. The primary messaging patterns include synchronous communication (where the caller waits for a response) and asynchronous messaging (the service can send multiple messages simultaneously). We recommend switching to asynchronous as you move more applications to microservices.

Your team also needs to set up appropriate public APIs (for client application calls) and backend APIs (for interservice communication). A public API should be compatible with your mobile and web applications. When selecting an API for the backend, you need to factor in latency, network performance, and payload size.

REST over HTTP/HTTPS is usually the optimal pattern for the client side. As for the server side, your options include RESTful interfaces (focused on stateless communications and scalability) and RCP interfaces (oriented towards commands and operations).

Step 8: Migrate Data

The next step includes moving legacy databases, logic, and behaviors that support the application.

Some applications will also need to access old data from your monolith (primarily in a phased adoption approach). You need to configure an API to gather information from other services. This way, the payment microservice can fetch data from the profile module in the monolith.

Step 9: Create a CI/CD Pipeline

You won’t get the most out of the new architecture without well-oiled continuous integration (CI) and continuous delivery (CD) processes. The CI allows your team to automatically test changes to always keep the code production-quality. CD tools help your teams automatically publish the code changes to the production environment.

Step 10: Implement and Deploy

Deploy the functionality gradually to ensure everything works as expected in the new architecture. Unfortunately, you might identify a significant semantic difference between the legacy system and the new one. Here’s how you can solve these problems.

• Use an anti-corruption pattern (glue code) — a layer that translates communication between the existing monolith and a new system. It helps you transfer only the data required by the microservice, basically filtering unnecessary data that might pollute your system.
• The canary release technique can help you reduce performance issues and errors when moving from monolith to microservices. Let’s say you migrated the application with a phased approach. First, send the traffic to the new microservice to a limited number of users (5%). If there are no errors, you can progressively increase the user count up to 100% before switching fully to a microservice.
• After refactoring the application into a consistent microservice, you can remove the glue code and retire the monolith components. Then, rinse and repeat until everything finds its way to your scalable architecture.

We have so far discussed what are microservices, when and how to migrate from Monolith to Microservices. In my next article, I’ll be discussing more on most commonly used migrations patterns from Monolith to Microservices.

About the Author

Priya Ekbote is the Executive Vice President of our Digital transformation practice.

With over 25 years of experience, this forward-thinking expert excels in leading software development teams, showcasing a proven knack for problem identification, analysis, and resolution to enhance customer satisfaction and cost control.

Serving as a liaison among stakeholders, she adeptly identifies and defines business needs, providing recommendations for solutions that propel the organization towards its goals. Driving Digital Transformation through highly valued change and innovation with proven versatility to bring fresh perspective, new ideas, and keen business intuition to spot growth opportunities.

She has directed Global Delivery Centre and Centre of Excellence (CoEs) to serve the global markets with cutting edge technologies and business transformation initiatives. Her extensive international experience involves working with clients, showcasing a high level of expertise in managing geographically dispersed teams and projects across diverse cultures throughout her 18-year association with Aress.

Under Priya’s expert guidance, our Digital transformation practice is thriving. Reach out to Priya today to see how her leadership can drive your business forward.